JP2000168601A - Electrically-driven power steering control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically-driven power steering control device which can exhibit a steering characteristic with no sense of congruity and which does not cause vibration and noise even upon stationary turning. SOLUTION: This electrically-driven power steering device is composed of a digital microcomputer as a core component. Further, a variation rate of a motor current I' with respect to a torque signal T is set to be constant during stationary turn so that there is no intermediate hold point such that the variation rate varies step-likely, and accordingly, no vibration and noise are caused during stationary turn which requires a large output power. Meanwhile, at a speed higher than 10 km/h, even though an intermediate fold point occurs as to a relationship between the toque signal T and the motor current I', a large output power is not produced so that the steering becomes smooth, and accordingly, no vibration and noise are caused. Further, a steering characteristic nearly equal to a steering characteristic of a hydraulic power steering device can be exhibited, and accordingly, even a driver who customs a hydraulic power steering device does not feel sense of congruity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of an electric power steering device for a vehicle.

[0002]

2. Description of the Related Art In a conventional vehicle equipped with an engine, a hydraulic pump which employs a hydraulic motor as a power assist motor has been widely used because a hydraulic pump driven by the engine could be provided. Was. However, in an electric vehicle without an engine or in a hybrid car using an engine only intermittently, a hydraulic motor cannot be used, so an electric power steering device using an electric motor as a power assist motor is used. . It is considered that the transition from conventional cars to electric cars and hybrid cars will further progress in the future.

[0003] Here, when switching from a conventional car that has already become widespread to an electric car or a hybrid car, if the steering characteristics of the power steering apparatus are greatly changed, the driver may feel uncomfortable. Is generated. Therefore, it is desirable that the electric power steering device has a steering characteristic close to that of the hydraulic power steering device to which the driver is already familiar.

The prior art 1 is disclosed in Japanese Patent Laid-Open No. 6-8835.
There is a technology of an electric power steering device disclosed in Japanese Patent Application Laid-Open Publication No. H11-163,873. According to the technology, a motor current command value corresponding to a steering torque and a vehicle speed is output from a control device by digital calculation by a microcomputer from a torque signal and a vehicle speed signal. According to this technique, as indicated by a broken line in FIG. 3, the motor current command value for the torque signal is a linear function within a predetermined range, and the rate of change of the motor current command value is constant. Therefore, a steering characteristic considerably different from the steering characteristic of the hydraulic power steering device shown by a solid line in the figure is obtained, and a driver who is familiar with the conventional hydraulic power steering device feels a sense of strangeness in the steering feeling. Inconveniences that occur.

On the other hand, Japanese Patent Application Laid-Open No.
There is a technology of an electric power steering device disclosed in Japanese Patent No. 2883. In this technology, an analog circuit using an operational amplifier and the like is used to convert the torque signal and the vehicle speed signal into analog signals.
A motor current command value corresponding to the steering torque and the vehicle speed is output from the control device. According to the technology, FIG.
As shown by a dashed line in FIG. 2, the motor current command value for the torque signal is obtained by continuously connecting two linear functions within a predetermined range at a break point. Therefore, in the prior art 2, since the steering characteristic approximate to the steering characteristic (solid line) of the hydraulic power steering device is obtained, the driver who is used to the hydraulic power steering device does not feel uncomfortable.

However, in the prior art 2, since the electric power steering control device is constituted by an analog circuit, a considerable number of man-hours are required for adjustment before shipment. Therefore, in spite of the fact that the control device is constituted by an analog circuit which is less expensive than a microcomputer, the expected cost reduction effect cannot be obtained. Further, with the cost reduction of microcomputers, which is accelerated year by year, it is becoming possible to configure a control device relatively inexpensively even with microcomputers that perform digital operations. Microcomputers have the advantage that they do not require individual adjustment at the time of shipment, and that there is no aging or temperature change in the steering characteristics. Therefore, it is possible to configure a control device having the characteristics of the prior art 2 using a microcomputer as a core. According to the configuration, it is considered that there is an advantage in terms of prevention of temperature change and aging change of the steering characteristics and cost reduction.

However, if the characteristics of the prior art 2 are realized by a control device having a microcomputer as a core, an operation time delay peculiar to the microcomputer will inevitably occur. Here, at the time of stationary operation and low speed with a large gain, the gradient of the motor current command value with respect to the torque signal changes suddenly at the middle break point, and at the middle break point, a certain motor current command value has already been generated. Therefore, when the vehicle is stationary or at a low speed, vibrations are generated near the middle break point due to the calculation time delay, and there is a new disadvantage that unpleasant vibration and noise are generated.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electric power steering control device which does not generate unpleasant vibrations or noises even when the vehicle is stationary, while providing steering characteristics without a feeling of strangeness. Tasks to be done.

[0009]

In order to solve the above problems, the inventor has invented the following means. (First Means) A first means of the present invention is an electric power steering control device according to the first aspect. That is, this means has a microcomputer at its core that performs digital operations. When the vehicle speed signal is less than a predetermined value, the microcomputer outputs a motor current command value with a constant rate of change of the motor current command value with respect to the torque signal within a predetermined range of the torque signal. On the other hand, when the vehicle speed signal is equal to or more than the predetermined value, the rate of change of the motor current command value with respect to the torque signal within the predetermined range of the torque signal is appropriately changed according to the vehicle speed signal.
Outputs the motor current command value.

In this means, when the vehicle is stationary, since the vehicle speed signal is less than the predetermined value, the motor current command value is output with the rate of change of the motor current command value with respect to the torque signal being constant within the predetermined range of the torque signal. . Therefore, when the motor current command value of a significant value is output, there is no break in the relationship between the motor current and the torque signal. Occasionally no unpleasant vibration or noise is generated. Further, it has been found from experiments by the inventors that the driver does not feel uncomfortable when the steering characteristic is considerably different from that of the hydraulic power steering device at the time of stationary steering. Therefore, at the time of stationary operation, even if the rate of change of the motor current command value with respect to the torque signal is constant,
The driver does not feel uncomfortable with the steering characteristics.

On the other hand, in a normal road running state, the rate of change of the motor current command value with respect to the torque signal within the predetermined range of the torque signal is appropriately adjusted in accordance with the vehicle speed signal because the vehicle speed signal is equal to or higher than the predetermined value. Can be changed. And
Since the motor current command value is output with a steering characteristic close to that of the hydraulic power steering device, the driver does not feel uncomfortable with the steering characteristic during normal traveling. Further, if the vehicle speed is sufficiently high, even if the rate of change of the motor current command value with respect to the torque signal suddenly changes in the middle, there is almost no unpleasant vibration or noise. This is because the gain of the steering characteristic is suppressed to a low value at a speed equal to or higher than a predetermined speed, so that even when a calculation delay at a realistic level occurs, the occurrence of self-excited vibration is sufficiently suppressed. .

Therefore, according to the electric power steering control device of the present invention, as compared with the prior art 1, there is an effect that the steering characteristic without a sense of incongruity can be obtained and unpleasant vibration and noise are not generated even when the vehicle is stationary. is there. Also,
Compared to the prior art 2, since the adjustment man-hour before shipping is almost omitted, there is an effect that the product price is rather reduced.

(Second Means) A second means of the present invention is an electric power steering control device according to the second aspect. That is, in this means, the microcomputer comprises: a torque signal phase compensation calculation unit; a first motor current calculation unit and a second motor current calculation unit; a weight calculation unit and a motor current weight calculation unit; a vehicle speed coefficient calculation unit and a motor current It has a vehicle speed calculator.

Here, the torque signal phase compensation calculating section has an action of compensating by advancing the phase of the torque signal from the steering torque sensor. The first motor current calculation unit is a calculation unit that calculates a constant change rate of the motor current command value with respect to the torque signal when the torque signal phase-compensated by the torque signal phase compensation calculation unit is within a predetermined range. is there. On the other hand, the second motor current calculation unit is a calculation unit that appropriately changes the rate of change of the motor current command value with respect to the torque signal when the phase-compensated torque signal is within a predetermined range. That is, the second motor current calculation unit has an effect of making the relationship between the torque signal and the motor current command value close to the steering characteristics of the hydraulic power steering device.

[0015] The weighting calculation unit may appropriately set a weighting coefficient so as to change the weighting between the output of the first motor current calculation unit and the output of the second motor current calculation unit in accordance with the vehicle speed signal. It is. The motor current weighting calculation unit is a calculation unit that weights according to the weighting coefficient and linearly combines the output of the first motor current calculation unit and the output of the second motor current calculation unit for output.

Further, the vehicle speed coefficient calculating section is a calculating means for appropriately setting a vehicle speed coefficient according to the vehicle speed signal in order to properly correct the output of the motor current weighting calculating section. The motor current vehicle speed calculation unit is a calculation unit that corrects the output of the motor current weight calculation unit according to the vehicle speed coefficient. In this means, the phase of the torque signal is compensated in the direction of the phase advance by the torque signal phase compensation calculation unit having a partially differentiating action so as to obtain a sharp steering characteristic at the time of sudden steering. Therefore, a sharp steering characteristic can be obtained even at the time of sudden steering. Further, the first motor current calculation unit calculates the motor current for the extremely low speed including the stationary operation, and in parallel, the second motor current calculation unit calculates the motor current for the high speed traveling. The value of the motor current for extremely low speeds and the value of the motor current for high speed traveling are appropriately weighted depending on the vehicle speed by the weighting calculation unit, and are linearly combined by the motor current weighting calculation unit. . Further, the vehicle current coefficient calculation unit corrects the linearly coupled motor current by the motor current vehicle speed calculation unit according to the vehicle speed coefficient set so that the steering wheel becomes appropriately heavy as the vehicle speed increases, and outputs the corrected motor current as the motor current command value. You.

Therefore, according to this means, in addition to the effect of the above-mentioned first means, there is an effect that the operation of the above-mentioned first means can be obtained by a simple operation means or a combination of operation logics. (Third Means) A third means of the present invention is the electric power steering control device according to the third aspect. That is, in this means, in the above-mentioned second means, the second motor current calculation unit calculates a motor current command value for the phase-compensated torque signal by a plurality of continuous linear functions.

Therefore, in the second motor current calculation section of the present means, if there is a dead zone, the motor current command for the phase-compensated torque signal is determined by combining at least two linear functions per quadrant. The value is determined. As a result, the logic of the second motor current calculation unit is simplified, and a practical but relatively inexpensive product can be provided.

Therefore, according to this means, in addition to the effect of the above-described second means, the logic of the second motor current calculation section is simplified, and a practical but relatively inexpensive product can be provided. This has the effect. (Fourth Means) A fourth means of the present invention is the electric power steering control device according to the fourth aspect. That is, in this means, in the above-mentioned second means, the second motor current calculation section calculates a motor current command value for the phase-compensated torque signal by a function in which a numerical value and a slope are continuous.

Therefore, the second motor current calculating section of the present means can approximate the steering characteristics of the hydraulic power steering device with a relatively simple function, and can provide a practically relatively inexpensive product. Become like Therefore, according to this means, in addition to the effect of the above-described second means, there is an effect that a product can be provided at a relatively low price while being practical.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the electric power steering control device according to the present invention will be clearly and fully described in the following embodiments so that those skilled in the art can understand the present invention. Embodiment 1 (Configuration of Embodiment 1) As shown in FIG. 1, an electric power steering control apparatus according to Embodiment 1 of the present invention includes a microcomputer 100 at its core. further,
The electric power steering control device of this embodiment has a torque signal input unit 1 and an A / D converter 2, a vehicle speed signal input unit 6, an A / D converter 7, and a D / A converter 12.

Torque signal input unit 1 and A / D converter 2
Is input means for inputting a torque signal T from a steering torque sensor (not shown) to the microcomputer 100. Further, a vehicle speed signal input unit 6 and an A / D converter 7
Is input means for inputting a vehicle speed signal V from a vehicle speed sensor (not shown) to the microcomputer 100. On the other hand, D
The / A converter 12 is an output unit that converts the motor current command value I output from the microcomputer 100 as a digital signal into an analog signal, and outputs the analog signal to a motor drive unit which is an inverter circuit including a power transistor and the like. is there.

That is, the electric power steering control device of the present embodiment includes a steering torque sensor (not shown).
, And a vehicle speed signal V from a vehicle speed sensor (not shown). Then, from the electric power steering control device of the present embodiment, a motor current command value I for setting the motor current of the power assist motor (not shown) is output to the motor drive unit.

When the vehicle speed signal V is less than a predetermined value, the microcomputer 100 sets the rate of change of the motor current command value I with respect to the torque signal T within a predetermined range of the torque signal T, and sets the motor current command value I to be constant. Has action to output. On the other hand, when the vehicle speed signal V is equal to or greater than the predetermined value, the rate of change of the motor current command value I with respect to the torque signal T is appropriately changed within the predetermined range of the torque signal T in accordance with the vehicle speed signal V. It has the function of outputting the value I. Such an operation is obtained as a combination of the operations of the following operation units.

That is, the microcomputer 100
Are a torque signal phase compensation operation unit 3, a first motor current operation unit 4 and a second motor current operation unit 5, a weight operation unit 8 and a motor current weight operation unit 9, a vehicle speed coefficient operation unit 10 and a motor current vehicle speed And an operation unit 11. Each of the arithmetic units described above is built and executed in the microcomputer 100 as software, and performs the following operations.

First, the torque signal phase compensation calculator 3 performs a phase compensation for advancing the phase of the torque signal T from a steering torque sensor (not shown) by a partial differential action corresponding to the transfer function (1 + gs) / (1 + ts). Has an action.
By this phase compensation action, the microcomputer 10
The calculation time delay of 0 is compensated for, and an agile response characteristic can be obtained even for sudden steering.

Next, if the torque signal T phase-compensated by the torque signal phase compensation computing section 3 is within a predetermined range, the first motor current computing section 4 calculates the motor current command value Is with respect to the torque signal T. This is a calculating means for calculating with a constant rate of change. That is, as shown in the graph in the block of the first motor current calculation unit 4, when the absolute value of the torque signal T is less than T _1, the motor current Is dead zone a zero is formed. However, the absolute value of the torque signal T when in the predetermined range of less above T ₁ T _3, the change rate of the motor current instruction value Is for the torque signal T is calculated as a constant. That is, when the absolute value of the torque signal T is in the same predetermined range, the motor current command value Is is calculated as a linear function rising from zero at a predetermined slope. The absolute value of the torque signal T is in T ₃ or more regions, the motor current Is is calculated as a constant value I ₂ which is continuous to the linear function.

On the other hand, the second motor current calculating section 5 is a calculating means for appropriately changing the rate of change of the motor current command value Ia with respect to the torque signal T when the phase-compensated torque signal T is within a predetermined range. is there. That is, the second motor current calculator 5 calculates the motor current command value Ia with respect to the absolute value of the phase-compensated torque signal T by two continuous linear functions, as shown in the graph in the block.

[0029] To explain more specifically, the second motor current calculating unit 5, like the first motor current calculating unit 4 described above, the absolute value of the motor current in the case of less than T ₁ I of a torque signal T
s is zero, forming a dead zone. However, when the absolute value of the torque signal T is within a predetermined range below above T ₁ T ₃ is the motor current instruction value Is for the torque signal T
Is calculated in such a manner that the rate of change is increased stepwise in two steps.

That is, in the first half (T ₁ ≦ T <T ₂ ) of the case where the absolute value of the torque signal T is within the same predetermined range,
The motor current command value Is is calculated as a linear function that rises from zero with a relatively gentle constant gradient. On the other hand, in the latter part (T ₂ ≦ T <T ₃ ) of the case where the absolute value of the torque signal T is within the same predetermined range, the torque function is calculated as a linear function rising with a relatively steep constant slope. Here, Where torque signal T is T _2, the value of both primary function is continuous.

[0031] In the region absolute value of T ₃ or more torque signal T, similarly to the first motor current calculating unit 4 described above, the motor current Ia is calculated as a constant value I ₂ which is continuous to the linear function You. As a result, the second motor current calculator 5
Has the effect of bringing the relationship between the motor current command value Ia and the torque signal T closer to the steering characteristics of a conventional hydraulic power steering device.

Further, the weighting calculating section 8 changes the weighting of the output Is of the first motor current calculating section 4 and the output Ia of the second motor current calculating section 5 according to the vehicle speed signal V so as to change the weighting coefficient k. _This is an arithmetic means for setting ₁ appropriately. Then, the motor current weighting calculating section 9 weights according to the weighting coefficient k _1,
And the output Is of the second motor current calculator 5 is linearly combined and output. The calculation method of the linear combination is performed according to the following equation 1, as described in the block of the motor current weight calculation unit 9.

[0033]

I ′ = (1−k ₁ ) × Is + k ₁ × Ia Here, the weighting coefficient k ₁ set by the weighting calculation unit 8 is such that the vehicle speed signal V is zero as shown in the graph in the block. During a period of less than 10 km / h, the value increases linearly from zero, and is set to a constant value of 1 at 10 km / h or more. Note that the signal from the rotation speed sensor of the ABS is used as the vehicle speed signal V. Since the accuracy of the vehicle speed signal V at low speed is low, the vehicle speed signal V is regarded as zero in a region where the vehicle speed is less than 5 km / h. It is.

[0034] Therefore, as shown by a solid line in FIG. 2, at a speed range of less than the vehicle speed 5km / h from the state outright laid vehicle speed 0 km / h is the region an absolute value is less than above T ₁ T ₃ of the torque T , The output I 'increases as a linear function without a break point. This graph shows the output Is of the first motor current calculation unit 4.
Is weighted by 1 and the output Ia of the second motor current calculation unit 5
Is not weighted at all, and the first motor current calculation unit 4
Is output from the motor current weighting calculator 9 as it is. Here, the output I ′ is a numerical value corresponding to the motor current, but is a numerical value in the process of calculating the current command value I to the motor drive unit.

The vehicle speed signal V gradually increases, and the vehicle speed 5
km / h, as indicated by the dashed line in FIG.
The output Is of the first motor current calculation unit 4 and the output Ia of the second motor current calculation unit 5 are weighted by a factor of five. As a result, the output I ′ having a slight turning point at the torque T ₂
Is output from the motor current weighting calculation unit 9. When the vehicle speed reaches 10 km / h or more, the weight coefficient k ₁ is set to ₁ by the weight calculation unit 8. As a result, the graph of the output I ′ of the motor current weighting calculation unit 9 shows that the output I ′ having a clear break point at the torque T ₂ (corresponding to the output I ₁ ) as shown by the broken line in FIG. Are output from the motor current weighting calculator 9. This graph shows that the output Is of the first motor current calculator 4 has no weight, the output Ia of the second motor current calculator 5 has a weight of 1, and the output Ia of the second motor current calculator 5 Are output from the motor current weighting calculation unit 9 as they are.

Thereafter, the output I 'of the motor current weighting calculator 9 is further multiplied by the vehicle speed coefficient k ₂ set by the vehicle speed coefficient calculator 10 by the motor current vehicle speed calculator 11 to obtain the motor current command value I. Is output as That is,
Vehicle speed coefficient calculation unit 10, in order to properly correct the output of the motor current weighting calculation unit, a calculation means for setting properly the vehicle speed coefficient k ₂ corresponding to the vehicle speed signal. The motor current vehicle speed calculation unit 11 is a calculation unit that corrects the output I ′ of the motor current weight calculation unit 9 according to the vehicle speed coefficient k ₂ .

Therefore, the microcomputer 100
, A motor current command value I is output as a digital signal, and the motor current command value I is converted into an analog voltage signal via the D / A converter 12 and transmitted to the motor drive unit. (Operation and Effect of First Embodiment) The electric power steering control device of the present embodiment is configured as described above, and exhibits the following operation and effect.

First, the phase of the torque signal T is compensated in the direction of the phase advance by the torque signal phase compensation calculation unit 3 having a partially differentiating action so that sharp steering characteristics can be obtained at the time of rapid steering. Therefore, a sharp steering characteristic can be obtained even at the time of sudden steering. Next, the first motor current calculation unit 4 outputs a motor current Is suitable for extremely low speeds including stationary operation.
In parallel, the second motor current calculation unit 5 calculates a motor current suitable for normal traveling at a vehicle speed of 10 km / h or more. The value of the motor current Is for the extremely low speed and the value of the motor current Ia for the normal running are appropriately weighted by the weight calculation unit 8 depending on the vehicle speed, as described above. The linear combination is performed by the operation unit 9. Further, the vehicle current coefficient I ′ linearly coupled is corrected by the vehicle current coefficient calculation unit 11 by the vehicle speed coefficient calculation unit 10 using the vehicle speed coefficient k ₂ set so that the steering wheel becomes moderately heavy as the vehicle speed increases. It is output as a current command value I.

That is, when the vehicle is stationary, the vehicle speed signal V is less than the predetermined value (5 km / h). Therefore, the motor current command value I for the torque signal T within the predetermined range (T _{1 to} T ₃ ) of the torque signal T is determined. The motor current command value I is output with the rate of change kept constant. Therefore, as shown by the solid line in FIG.
When the motor current command value I having a significant value is being output, there is no break in the relationship between the torque signal T and the motor current. Therefore, even if the control is performed by the microcomputer 100 with a delay in the operation time, unpleasant vibration or noise does not occur at the time of stationary operation.

Further, it has been found from experiments by the inventors that the driver does not feel uncomfortable when the steering characteristic is considerably different from that of the hydraulic power steering device during stationary operation. Therefore, even when the rate of change of the motor current command value I with respect to the torque signal T during the stationary operation is constant, the driver does not feel uncomfortable about the steering characteristics.

On the other hand, in a normal running state in which the vehicle speed is 10 km / h or more, since the weight coefficient k ₁ is 1, the motor current with respect to the torque signal T within a predetermined range (T _{1 to} T ₃ ) of the torque signal T is set. The rate of change of command value I is appropriately changed according to vehicle speed signal V. Then, in response to the input of the torque signal T, the motor current command value I is output with a polygonal steering characteristic close to that of the hydraulic power steering device.
During normal traveling, the driver does not feel uncomfortable with the steering characteristics.

If the vehicle speed is 10 km / h or more,
As shown by the dashed line in FIG. 2, despite the fact that the rate of change of the motor current command value I with respect to the torque signal T suddenly changes in the middle, there is almost no unpleasant vibration or noise. This is because, at or above a predetermined speed, the gain of the steering characteristic is suppressed to a low level by the vehicle speed coefficient calculation unit 10, so that even when a calculation delay at a realistic level occurs, the occurrence of self-excited vibration is sufficiently low. It is because it is suppressed.

Further, according to experiments by the inventors, the relationship between the torque signal T and the motor current command value I is not broken as in the case of the characteristic of the hydraulic power steering apparatus. Have not been found to feel uncomfortable. Therefore, it has become clear that it is not necessary to set the relationship between the torque signal T and the motor current command value I with a line graph or curve having a greater number of break points. As a result, the electric power steering control device of the present embodiment can be operated without increasing the calculation load of the microcomputer 100 so much that it is practical.

Since the second motor current calculating section 5 also has a dead zone, the motor current command value I for the phase-compensated torque signal T is determined by a combination of two linear functions for each quadrant, and the hydraulic power Characteristics similar to those of the steering device are obtained. As a result, the logic of the second motor current calculation unit 5 becomes simple, and the microcomputer 100 that is practical and relatively inexpensive can be employed.

The vehicle speed is 5 km / h or more and 10 km / h.
In the following transition state, the relationship between the torque signal T and the motor current command value I changes stepwise according to the vehicle speed between the dashed line and the broken line in FIG. In addition, the first motor current calculator 4 and the second motor current calculator 5 of the present embodiment are provided with dead zones on both sides of the zero point, so that when the steering column (not shown) is in the neutral state, a good condition is obtained. Straightness is obtained.

Summarizing the above, according to the electric power steering control device of the present embodiment, firstly, uncomfortable vibration and noise even at the time of stationary installation can be obtained while obtaining steering characteristics that are less uncomfortable than the prior art 1. This has the effect of not generating any. Secondly, since the logic of the microcomputer 100 is relatively simple, and the number of adjustment steps before shipment is almost eliminated as compared with the prior art 2, there is an effect that the product price is rather reduced. Third, prior art 2
Since there is a dead zone including the zero point of the torque signal T, there is also an effect that the straightness of the vehicle is good when the steering column is neutral.

(Modification 1 of Embodiment 1) As Modification 1 of the present embodiment, the number of middle break points of the second motor current calculation unit 5 is increased to a plurality, and the characteristics of the hydraulic power steering device are reproduced more faithfully. It is also possible to implement an electric power steering control device. According to this modification, there is an effect that even a driver who is considerably sensitive to a change in the steering characteristics can steer without a sense of incongruity.

(Modification 2 of Embodiment 1) As Modification 2 of the present embodiment, the second motor current calculator 5 calculates the motor current command value Ia corresponding to the phase-compensated torque signal T such that the numerical value and the slope are continuous. It is possible to implement the electric power steering control device calculated by the function. In the second motor current calculation unit 5 of the present modification, the steering characteristics of the hydraulic power steering device can be more accurately approximated by a relatively simple function such as a quadratic function or a cubic function connected to the dead zone. As a result, according to the present modified embodiment, there is an effect that even a driver who is considerably sensitive to a change in the steering characteristics can steer without a sense of incongruity.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an electric power steering control device according to a first embodiment.

FIG. 2 is a graph showing characteristics of the electric power steering control device according to the first embodiment.

FIG. 3 is a graph showing steering characteristics of the prior arts 1 and 2;

[Explanation of symbols]

100: microcomputer 3: torque signal phase compensation operation unit 4: first motor current operation unit 5: second motor current operation unit 8: weight operation unit 9: motor current weight operation unit 10: vehicle speed coefficient operation unit 11: motor current Vehicle speed calculation unit 1: Torque signal input unit 2: A / D converter 6: Vehicle speed signal input unit 7: A / D converter 12: D / A converter

Claims (4)

[Claims] An electric power steering control device which receives a torque signal from a steering torque sensor and a vehicle speed signal from a vehicle speed sensor and outputs a motor current command value for setting a motor current of a power assist motor to a motor drive unit. In the above, when the vehicle speed signal is less than a predetermined value, the rate of change of the motor current command value with respect to the torque signal is constant within a predetermined range of the torque signal, and when the vehicle speed signal is equal to or more than the predetermined value, An electric power steering device comprising: a microcomputer for performing a digital operation for appropriately changing the rate of change of the motor current command value with respect to the torque signal within a predetermined range of the torque signal in accordance with the vehicle speed signal. Control device. 2. The microcomputer according to claim 1, further comprising: a torque signal phase compensation calculating section for advancing the phase of the torque signal to compensate for the torque signal. Within the predetermined range of the torque signal, a change rate of the motor current command value with respect to the torque signal. A first motor current calculation unit that calculates the constant as a constant; a second motor current calculation unit that appropriately changes the rate of change of the motor current command value with respect to the torque signal within the predetermined range of the torque signal; A weight calculation unit for appropriately setting a weight coefficient according to the vehicle speed signal; a motor current weighted according to the weight coefficient to linearly combine an output of the first motor current calculation unit and an output of the second motor current calculation unit. A weight calculation unit, a vehicle speed coefficient calculation unit for appropriately setting a vehicle speed coefficient according to the vehicle speed signal, and a motor current weight calculation The electric power steering control device according to claim 1, further comprising: a motor current vehicle speed calculating unit that corrects an output of the unit according to the vehicle speed coefficient. 3. The electric power steering control device according to claim 2, wherein the second motor current calculation section calculates the motor current command value for the torque signal by a plurality of continuous linear functions. 4. The electric power steering control device according to claim 2, wherein the second motor current calculation unit calculates the motor current command value for the torque signal by a function having a numerical value and a continuous slope.